You would need a way to select which of your thoughts flow to the computer.

Even if you had no thoughts that you want to keep secret, many thoughts would not be relevant to the task at hand and could cause it to respond to things that you don't want to.

The mechanism to allow you to channel thoughts shouldn't make the HCI slower than other input types.

They have to exist first.

I hope I’m retired before anything like this becomes a reality. The idea that a person needs brain surgery to compete in the job market… that’s not something I want any part of. As an idea for science fiction, The Matrix was neat, but it’s not a reality I want to see.

Pretending this is a real thing for the sake of discussion, is maximizing productivity really such a important thing that it would be worth undergoing extremely invasive surgery to implant an extremely invasive device for? If so, I think that we've gone very far wrong in society.

In any case, I'm certainly not going to say that people shouldn't be able to do whatever they want to their own bodies, no matter how foolish I think it may be.